1. Technical Field
The present invention relates to a liquid container of an air-open type that is suitably used as an ink cartridge to be detachably mounted on an ink jet printer, and in particular, to a technique that can a good ink sweeping capability and suppress bubble leakage.
2. Related Art
In an ink jet printer, an ink jet type printing head that causes ink droplets to be ejected from nozzle openings by applying a pressure to a pressure generating chamber communicating with a common ink chamber and the nozzle openings, and an ink cartridge that supplies ink to the printing head are mounted on a carriage. Then, the ink droplets are ejected onto a recording paper according to printing data, while the carriage reciprocates.
By the way, the nozzle openings of the printing head are located at positions lower than a liquid level of ink of the ink cartridge. Accordingly, since a head pressure acts on the nozzle openings, in general, in order to prevent bleeding of ink from the nozzle openings, a porous body is accommodated in the ink cartridge, and a pressure of the ink cartridge is slightly lower than the nozzle openings according to a surface tension by the porous body.
By the way, if the quantity of ink absorbed by the porous body decreases along with ink consumption, the surface tension of the porous body increases, and thus the supply of ink to the printing head may be delayed, and ink in the ink cartridge may be not completely consumed. In addition, since ink that can be contained in the cartridge decreases by the amount corresponding to the substantial volume of the porous body, the ink cartridge may become large.
In order to solve such an inconsistency, there is an ink cartridge for an ink jet printer disclosed in Patent Document 1.
In the ink cartridge for an ink jet printer, a container having an ink supply port at its bottom surface is divided such that an ink chamber and an ink supply chamber are formed on upper and lower sides by a film valve seat formed of an elastic thin film having a through hole at its central portion. Further, a valve body is provided at a position facing the through hole, and the film valve seat is brought into contact with the valve body by a difference in pressure of the ink chamber and the ink supply chamber.
Accordingly, a differential pressure is applied to the film valve seat over a wide area, and thus a flow passage from the ink chamber to the ink supply chamber is opened corresponding to slight ink consumption. Then, ink is discharged to the printing head, without applying an excessive negative pressure to the printing head, and an increase in pressure of the ink supply chamber is absorbed into the ink chamber by deformation of the film valve seat. Therefore, ink of the ink chamber can be stably and reliably supplied to the printing head, without using the porous body.
Patent Document 1:JP-A-8-174860
In the above-described known ink cartridge for an ink jet printer, the film valve seat is provided, and the inside of the liquid containing portion is divided by many partition walls so as to form the flow passage. Then, a negative pressure is generated, without providing the porous body in the liquid containing portion, such that the quantity of ink to be contained increases. In this case, however, ink may remain at corners of the liquid containing portion or complex parts, and thus residual ink may occur. In addition, since the porous body is removed, when the ink cartridge in use is separated from the carriage and vibrates or when the ink cartridge is erroneously dropped, air in the liquid containing portion may flow downstream, and bubbles flow into the printing head. As a result, bubble leakage resistance becomes low.